If you are to totally remove ...

If you are to totally remove all chlorine for purified water then you will need both.  In which case you will normally dose bisulphite first then use the carbon to mop up any residual chlorine.  There is a price for using carbon.  Firstly, it is a fixed bed and will need to be re-activated or replaced.  Secondly bacteria grow on the carbon and will release into the water.  If you are producing water for injections, this can cause pyrogenic reactions.  In which case it could be followed up by AFM (active filtration media) which will remove the residual bacteria, which have become released from the carbon.  If you use bisulphite and the water stands for a period of time, anaerobic sulphur bacteria will develop.